Rhesus Macaque mRNA Vaccine Evaluation

The groups consisted of three female and three male Indian rhesus macaques (Macaca mulatta), 2–3 years of age, weighing 3–6 kg. Prior to vaccination or bleedings, macaques were ketamine-anesthetized or with a mixture of ketamine/dexmedetomidine with atipamezole reversal and monitored regularly until fully recovered from anesthesia. In brief, macaques were injected IM into the deltoid muscle with 500 µL of mRNA or YF-17D vaccines. mRNA vaccine groups consisted of YF prM-E mRNA-LNP (10 or 20 µg), YF NS1 mRNA-LNP (10 µg), and a bivalent prM-E/NS1 vaccine (10 µg of each mRNA-LNP). The positive control group was vaccinated with a full human dose of the YF-17D licensed vaccine (17D-204, Stamaril^®, Sanofi Pasteur). One animal from the positive control group (animal r18015) presented diarrhea and Campylobacter coli infection and was treated with azithromycin for 5 days before the first vaccination. All mRNA vaccine groups were administered twice at a 4-week interval while the YF-17D vaccine was injected once. After vaccination, the site of injection was monitored for an inflammatory response. Blood draws were performed before the vaccination (weeks –2 and 0), post first vaccination (weeks 1, 3, and 4), post second vaccination (weeks 5, 6, 8, 12, 16, and 24) to collect serum for serology, and for the measurement of cytokines and chemokines before and 16 h after the first and second immunization (Supplementary Fig. 1d).